1. Field of the Invention
The present invention relates to a temperature regulating system for a vehicle. The invention will be described below for a case where the temperature regulating system is installed in a construction vehicle in the form of a wheel loader. This is a preferred, but in no way limiting, application of the invention.
An example of an application of the temperature regulating system is for heating/cooling a lubricating oil for the gearbox of the vehicle. This comprises (includes, but is not limited to) a number of interacting gear wheels. In order to reduce wear of these components during operation, they are lubricated with the oil. The lubricating oil functions worse when it is cold. It is therefore desirable, for example when the vehicle is cold-started, for it to be possible to heat the oil. After a period of operation of the gearbox, there is also a risk of the lubricating oil becoming so hot that the gearbox or the hydraulic system will be damaged. It is then desirable for it to be possible to cool the lubricating oil.
2. Background of the Invention
WO 99/43931 describes a temperature regulating system for a wheel loader. The system comprises a first hydraulic arrangement for providing the hydraulic cylinders of the vehicle, which drive the shovel of the vehicle, with hydraulic oil. The system also comprises an arrangement for cooling the internal combustion engine of the vehicle. The cooling arrangement is connected to the hydraulic arrangement via a first heat exchanger. A charge air cooler for the turbo compressor of the vehicle is located up-stream of the heat exchanger in the flow direction of the coolant in the coolant circuit.
This construction is advantageous, for example, when the internal combustion engine is cold-started. The charge air cooler cools the charge air as soon as the internal combustion engine is started, which results in rapid heating up of the hydraulic oil via the first heat exchanger.
During operation of the shovel, the hydraulic oil may become too hot to function effectively as a working fluid. The temperature regulating system is adapted to sense this and, in such a case, the oil is cooled. This is brought about by a further heat exchanger, namely the radiator of the vehicle, being arranged in the coolant circuit. In such a case, the coolant is cooled in this further heat exchanger.
WO 99/43931 also describes how the temperature regulating system can comprise a second hydraulic arrangement for providing the transmission of the vehicle with oil. The cooling arrangement is then connected to this second hydraulic arrangement via a second heat exchanger.
WO 99/43931 further describes how the temperature regulating system can comprise a third hydraulic arrangement for providing the axles of the vehicle with oil. The cooling arrangement is then connected to this third hydraulic arrangement via a third heat exchanger.
In different operating states, the various parts which require a supply of hydraulic oil are loaded to different degrees. One example of an operating state is short cycle load, in which the transmission of the vehicle is hot and the axles are cold. Another example of an operating state is transport driving, in which the axles of the vehicle are hot and the transmission is cold. When the operating state is changed, it is necessary to heat up the hydraulic oil to be supplied to the part used in the intended operating state before it will function optimally. It would therefore be desirable to produce a vehicle with improved energy utilization.